You could use size 5 crochet cotton from DMC instead of embroidery floss.
Embroidery floss is softer than the standard crochet cotton, it may not wear as well, but the amount of colors available is a plus.
When starting the beg ch, you can adjust the size of the ball by chaining the length from the point just under your index finger across to the bottom of your palm above your wrist x 2. I know this sounds funny, but it's 100% right, every time. :)